The use of the homopolymers of polyacrylic acid salts, modified copolymers of said salts, or the use of a combination of the two as dispersants for aqueous slurries of inorganic pigments is well known in the art.
U.S. Pat. No. 4,233,081, discloses a dispersing agent derived from the reaction of an alpha-hydroxy acrylic acid and inorganic bases such as hydroxides of alkali metals, ammonium hydroxide or organic nitrogen bases of the aliphatic type such as diethanolamine.
Japanese Pat. No. 63035899, discloses as dispersants the polymerization products of acrylic acid and methacrylate modified ethylene oxide/propylene oxide block copolymers which are subsequently neutralized yielding the corresponding salts.
Japanese Patent No. 620830028 discloses dispersants consisting of copolymers having repeating units including olefins, maleic anhydride, and poly(oxyalkylene) ester salts.
European Patent No. 296,610, discloses a glycol dispersion of calcium carbonate wherein the calcium carbonate is initially treated with polymers of alpha, beta-unsaturated carboxylic acids, esters of such acids, or salts, examples of which include, a 50:50 acrylic acid-polyethylene glycol monomethylacrylate copolymer. The treated calcium carbonate is then wet-ground in an equivalent weight of glycol to give a dispersion.
Japanese Patent No. 60001268, discloses a dispersant composition consisting of a condensed phosphoric acid salt and polyacrylic acid salt, and/or polyoxyethylene alkyl ether.
The dispersants employed in the present invention are mixtures or blends of water soluble polycarboxylates and nonionic polyether polyols.